Subj : Re: Study Suggests There Are 300 Million
To   : Tony Langdon
From : Charles Pierson
Date : Sat Nov 14 2020 06:24 am

Hello, Tony Langdon.
On 11/14/20 8:55 PM you wrote:

 TL> -=> On 11-13-20 06:11, Charles Pierson wrote to Tony Langdon <=-
 CP>> It really is. But with the distances involved, I suppose that 
 CP>> there isn't another way to do it.
 TL> Actually, there's several methods for discovering exoplanets, 
 TL> which include: Radial velocity - detecting the "wobble" of the 
 TL> star as planets orbit it.  And they can detect multiple planets 
 TL> here.  This works by using Doppler shift of the light from the 
 TL> star. Direct imaging - yes, in some rare cases, it is possible! 
 TL> Gravitational microlensing - seeing the effect of the planet's 
 TL> gravity on distant starlight passing by. Astrometry - Similar to 
 TL> radial velocity, except looking at how the position of the host 
 TL> star changes as it "wobbles" with the orbiting planets, instead of 
 TL> Doppler shift. And of course, we've been discussing the transit 
 TL> method in this thread. Ref:  
 TL> https://exoplanets.nasa.gov/alien-worlds/ways-to-find-a-planet/# 
 TL> There are other methods, but they are still fairly experimental. 
 TL> :)

I stand corrected, although, honestly, many of those methods do seem variations 
of a theme.

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Best regards!
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